PROJECT SUMMARY The incidence of autism spectrum disorders (ASD) has increased dramatically in the last decade. The latest report from the Centers for Disease Control and Prevention state that 1 in 59 children are being diagnosed with ASD and it is four times more prevalent in boys than girls. Common treatments for children with ASD are applied behavioral therapy, occupational and speech therapy, which are used solely or in combination. Hippotherapy (HPOT) is another treatment option that has been shown to positively impact various aspects of behavior. This pilot project aims to determine the effects of a 6-week HPOT program on movement and social behavior of children with ASD and to investigate the underlying mechanisms of why HPOT is successful for ASD through the coupling of physiological and temperamental responses between horse and rider. Our approach involves examining these skills pre, during, and post HPOT intervention in children diagnosed with ASD. A group of aged matched children with typical development will serve as the control group. Innovative measures of physiological coupling and temperament between horse and rider as well as objective and quantitative measures of movement and social behavior and caregiver perception will be collected. We anticipate that following completion of the proposed study, we will provide the necessary foundation to understand the mechanisms of HPOT, and thus provide a new framework to test clinical trials of HPOT and human-animal interaction, and ultimately improve the lives of those diagnosed with ASD and their families.